This invention is generally directed to processes for the preparation of halogenated chalcogens and halogenated chalcogenide alloys. More specifically, the present invention is directed to the preparation of chalcogenide alloys, and chalcogens with halogens, such as chlorine contained therein, by simultaneously coreducing the appropriate corresponding esters, and the halogenated analogs thereof. Accordingly, there is provided in accordance with the present invention a simple, economically attractive, low temperature process for the direct chemical preparation of halogenated chalcogens, inclusive of selenium, by the coreduction reaction of a chalcogen ester, and a chalcogen halide. The resulting halogenated chalcogens, and further chalcogenide alloys prepared in accordance with the process of the present invention are useful as photoconductive imaging members that can be selected for electrostatic imaging processes. In contrast to prior art processes, in accordance with the process of the present invention the halogen is homogeneously incorporated into the chalcogens or chalcogenide alloys, as well as being covalently bonded thereto. Thus, for example, in accordance with the process of the present invention the halogens are incorporated as stable halogen chalcogen, or halogen chalcogenide bonds.
The incorporation of halogens into selenium or selenium alloys, and their application as xerographic imaging members is well known. These members can be subjected to a uniform electrostatic charge to permit the sensitization of the surface of the photoconductive layer, followed by imagewise exposure to activating electromagnetic radiation which selectively dissipates the charge in the illuminated areas of the photoconductive member, and wherein a latent electrostatic image is formed in the non-illuminated areas. The resulting image may then be developed and rendered visible by depositing thereon toner particles. The aforementioned commercially available halogenated selenium or selenium alloys are generally substantially pure, 99.99 percent or greater, since the presence of impurities has a tendency to adversely effect the imaging properties of selenium, including the electrical properties thereof, causing copy quality to be relatively poor in comparison to devices wherein high purity components are used.
Also, known are layered organic and inorganic photoresponsive devices with amorphous selenium, trigonal selenium, amorphous selenium alloys, or halogen doped selenium alloys. One such photoresponsive member is comprised of a substrate, a photogenerating layer of a metal phthalocyamine, a metal free phthalocyanine, vanadyl phthalocyanine, or selenium tellurium alloys, and a transport layer with an aryl diamine dispersed in a resinous binder, reference U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference.
Further, many processes are known for the preparation of chalcogenide alloys, particularly selenium containing alloys including, for example, the melt blending of elemental substances, such as selenium and arsenic in the proportions desired in the final alloy product. Thus, for example, there is disclosed in U.S. Pat. No. 3,634,134 the preparation of arsenic-selenium alloys by mixing a master alloy with the appropriate proportions of arsenic and selenium. This method involves high temperatures, and in most instances, crystalline materials are not obtainable. Further, in some situations depending on the process parameters, there is generated with the melt blending process an inhomogeneous mixture of arsenic, selenium, and an arsenic selenium alloy. Additionally, in these processes, there must be selected for evaporation arsenic and selenium of a high purity, that is 99.99 percent; however, processes for obtaining these purities require undesirable high temperature distillations and costly equipment. A similar melt blending method for preparing selenium alloys is disclosed in U.S. Pat. No. 3,911,091. The alloys obtained may then be doped with halogens by, for example, a complex physical process wherein halogen gas is bubbled through the alloy melt.
Moreover, there is disclosed in U.S. Pat. No. 3,723,105 a process for preparing a selenium-tellurium alloy by heating a mixture of selenium and tellurium present in an amount of from 1 to 25 percent by weight to a temperature not lower than 350.degree. C., followed by gradual cooling of the molten selenium and tellurium to about the melting point temperature of the selenium tellurium alloy at a rate not higher than 100.degree. C. per hour; and subsequently quenching to room temperature within 10 minutes.
Additionally, there is disclosed in U.S. Pat. No. 4,121,981 the preparation of a selenium alloy by, for example, electrochemically codepositing selenium and tellurium onto a substrate from a solution of their ions wherein the relative amount of alloy deposited on the cathode is controlled by the concentrations of the selenium and the tellurium in the electrolyte, and by other electrochemical conditions. Once the selenium tellurium layer deposited on the cathode has reached the desired thickness, deposition is discontinued and the cathode is removed.
Also, there is disclosed in U.S. Pat. No. 3,524,745, the preparation of an arsenic antimony selenium alloy by heating a mixture of these materials at a temperature of 600.degree. C. for a period of several hours in a vacuum, followed by air cooling to room temperature. According to the teachings of this patent, the cooled alloy depending on the initial composition is a mixture of crystalline and amorphous phases, or completely amorphous.
Furthermore, there is illustrated in U.S. Pat. No. 4,484,945, the disclosure of which is totally incorporated herein by reference, a process for the preparation of chalcogenide alloys in high purity which comprises providing a solution mixture of oxides of the desired chalcogens, and subsequently subjecting this mixture to a simultaneous coreduction reaction. Similarly, in U.S. Pat. No. 4,460,408, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of chalcogenide allows in high purity which comprises providing pure esters of the desired chalcogenide; and subsequently subjecting the mixture of esters to a coreduction reaction.
Although these processes, as well as others, are suitable for their intended purposes, in most instances, excluding the process described in the U.S. Pat. Nos. 4,484,945 and 4,460,408, high temperatures and distillation steps are needed to generate the product desired. Further, in some instances, these processes result in selenium alloys which have differing electrical properties which is believed to be a result of inhomogenities known to exist in noncrystalline glasses. Also, many of the prior art halogenated alloy processes involve a physical process rather than the advantageous chemical method.
There thus continues to be a need for new improved processes of preparing halogenated chalcogens, and chalcogenide alloys. Additionally, there continues to be a need for an improved simple, economically attractive, direct process for the preparation of high purity halogenated chalcogens, and halogenated chalcogenide alloys of high purity. Also, there is a need for improved processes wherein binary halogenated chalcogenide and ternary halogenated alloys can be obtained in high purity by the selection of substantially similar process parameters. Additionally, there continues to be a need for improved processes of preparing halogenated chalcogenide alloys that are homogeneous, are of a crystalline form, and that can be obtained in various proportions without high temperatures. These needs can be satisfied in accordance with the process of the present invention wherein, for example, substantially halogenated homogeneous chalcogenide crystalline alloys result by the coreduction of a mixture of a chalcogenide ester, and the corresponding halogenated analog.